Abstract
The receptor-evoked Ca
signal in secretory epithelia mediate many cellular functions essential for cell survival and their most fundamental functions of secretory granules exocytosis and fluid and electrolyte secretion. Ca
influx is a key component of the receptor-evoked Ca
signal in secretory cell and is mediated by both TRPC and the STIM1-activated Orai1 channels that mediates the Ca
release-activated current (CRAC) I
. The core components of the receptor-evoked Ca
signal are assembled at the ER/PM junctions where exchange of materials between the plasma membrane and internal organelles take place, including transfer of lipids and Ca
. The Ca
signal generated at the confined space of the ER/PM junctions is necessary for activation of the Ca
-regulated proteins and ion channels that mediate exocytosis with high fidelity and tight control. In this review we discuss the general properties of Ca
signaling, PI(4,5)P
and other lipids at the ER/PM junctions with regard to secretory cells function and disease caused by uncontrolled Ca
influx.